Vineyards and orchards produce valuable fruit for eating and for making wine and other beverages. Particularly when the fruit is ripening it is subject to depredation by birds which can cause not only crop damage, but crop loss. As grapes and fruit ripen and sugar content increases, injured or damaged fruit becomes increasingly susceptible to bunch rot pathogens. The bunch rot complex of fungi and bacteria establish infections most often through a wound on the surface of fruit. These fungi and bacteria are commonly present on soil debris and many plant surfaces, including the fruit itself. Because of the close proximity of pathogens to fruit, the rot process can begin almost as soon as the skin of the grape is compromised. Any injury to the skin of ripening berries, grapes or other fruit from large to very small, is a potential entry point for these pathogens causing infection on the damaged fruit which can and does spread to adjacent otherwise undamaged fruit.
In the case of wine or table grapes, “bird peck” damage can be very costly, one grape with broken skin can lead to a fungal infection and loss of the whole grape cluster. It is difficult and thus relatively expensive to cull rotting grapes; such culling almost always necessitates removal of the infected grape cluster. There are two typical methods of culling, field culling from the vine and conveyor culling at the winery, both cumbersome and labor intensive. For grapes that are machine harvested, culling is not possible once the harvester removes the fruit and mixes the affected grapes in large gondolas that can hold tons. In such a case, a small amount of bird peck induced rot can cause large-scale crop rejections by the fruit buyer and or winery resulting in a severe economic loss to the grower.
Such bird induced damage to fruit can be reduced or prevented by a number of methods include killing the birds, scaring away the birds, trapping the birds, and providing barriers between the fruit and birds. Killing the birds is typically illegal and inhumane. Falconry, propane cannons, and passive means such as flash tape or balloons are utilized to scare the birds. If at all successful, these methods often only serve to temporarily move the birds to another location. Similarly, trapping the birds and temporarily removing them from the area has not proven effective.
Net-type barriers can offer complete and continuous barrier protection twenty four hours a day. With respect to vineyards, where grapes are grown in rows with multiple vines supported by trellis', the netting is typically utilized in one of three ways: 1) by draping netting over single or multiple rows of vines, 2) by securing netting in narrow panels along the sides of trellis rows to protect only the zone of the vine that bears fruit, or 3) by suspending the netting from a permanent overhead structure.
The most common method is to lay a net over the vine canopy, that is, simply over the entire vine. The efficiency of this method is facilitated by the great number of widths available, particularly for knitted nets. Such nets can cover two, three, four or more rows in one pass.
Growers who want to avoid covering the entire canopy with net can instead install narrow nets at the side of the canopy to cover the fruit zone. This practice is labor intensive, particularly where such installation and removal occurs annually. Such side net must be physically attached to the trellis that supports the row of vines at multiple points which greatly increases installation and removal costs.
Nets can also be used in constructing bird exclosures. Bird exclosures require a permanent support structure of posts and wires than can interfere with the functioning of other critical vineyard equipment such as harvesting machines. Exclosures also necessitate the use of heavier and more expensive netting.
There are four common types of netting used: extruded, warp knitted, and knotted or multi-filament knotless. One common type of modern commercial bird net is made as a single piece by extrusion. The resulting extruded net is stiff and has sharp edges requiring that workers wear leather gloves when working with it. Extruded net is stiff and has a property known as shape memory. Shape memory makes it difficult to pull the net in place. It must be manually secured below the fruiting zone, or it will revert to its original shape, lifting away from the fruit and allowing entry by birds from below.
The width of extruded net is limited to the width of the extrusion tooling. Extruded net is made in such a way that it generally must all be the same color, eliminating the potential for colored markers to be included in the manufacture of the net. Such colored markers can facilitate installation and removal by providing reference lines for positioning feedback when installing the net. The absence of such markers makes it hard to center the net over the canopy. Similarly, the edge cannot be made a contrasting color to make it easy for a worker to locate the edge. Extruded nets are handled on rolls, which are heavy; installation and removal require the use of heavy, expensive and potentially dangerous hydraulic equipment.
Extruded net offers the advantage that its dimensions are fixed; it cannot be stretched and therefore cannot be installed with the incorrect length or width.
Knitted net is more flexible than extruded net. A common form of knitting is warp knitting, with raschel knit being a class of fabrics of the warp type. Warp knits are characterized by the yarns, or threads, being formed into stitches in a lengthwise direction. Warp knitted net made from high density polyethylene, polypropylene, or nylon is supple and drapes easily in place. Such knitted netting does not have any shape memory, so it hangs all the way down to the ground protecting the vine, and in many applications does not need to be secured, unlike extruded net. Further, knitted net is soft to the touch and does not have sharp corners or edges to cut the hands of workers, so workers do not need gloves to protect their hands. Most single or double knitted net can be installed and retrieved with an inexpensive non-hydraulic applicator.
The same warp knitting machine can produce net from 1 foot to 100 feet wide. Warp knitted net is made with a wide variation in thread “denier” to create heavier or lighter weight nets. Further, warp knitted net has a rip-stop property, in that small tears caused by vineyard posts or other means do not propagate through the material.
Knotted and multi-filament knotless forms of net are highly effective alternatives to knitted and extruded net. Generally, these are used in permanent installations to create bird exclosures. The main disadvantage of knotted and knotless nets is their high cost.
Referring now to raschel knitted diamond or hexagonal mesh net, as currently manufactured this net is stretchy, or more precisely it is not dimensionally stable in either the lengthwise or widthwise direction. For example, when such a net is pulled lengthwise, the meshes in the net will deform and become long and narrow resulting in a narrowing of the potential width of the net. When the net is pulled tight, in the longitudinal direction, the meshes will essentially be closed; this defines the rope length of the net. The rope length can refer to the entire length of the net, for example 150 meters, or can refer to a unit length by reference to mesh opening density, for example 48 aligned openings per meter. Each of such nets have a “design” size where the individual openings defined by the meshing have the optimal size, which would normally be at or about the maximum opening area. The design size would have a design length, which can be stated as the entire length of the net, for example 100 meters and a design width, for example 5 meters, which would normally be at or about the labeled length and width assigned to the net by the manufacturer and put on the net packaging. The design length may also be stated in a unit length by reference to mesh opening density, for example, 32 aligned openings per meter.
Referring to FIG. 1, there can be seen a partial view of a prior art knitted net in a slack position with the meshes at approximately their optimal size. FIG. 1A shows a prior art net under tension in a lengthwise direction E such that the border rope is pulled taught and thus linear, the meshes are not of optimal size. As can be seen in FIGS. 1 and 1A, when the net is subjected to tension in the direction of arrow E, a dimension B, the width of the “square” or meshes is reduced to a dimension D. Further, a dimension A, the length of the meshes, is increased to a dimension C when under tension in the direction of arrow E. The dimensions of the individual meshes of course correspond to the length and width of the net when the meshing positioning is uniform. In such prior art netting there is no easy indicator as to the proper lengthwise tension or stretch to apply to the netting. The easiest stretch length is the taught “rope” length of the border bundle of meshes which results in a net stretched lengthwise more than the optimal “design” length and size.
When this type of net is installed, as the net is laid down over the canopy of trees or bushes (i.e., blueberries), vines or other crops (i.e. strawberries), the meshing immediately becomes engaged with the leaves and branches effectively preventing any longitudinal or lateral adjustment of the positioning of the net on the canopy. Thus, the net has to be close to its “design” size as it is deployed. Deployment in the design size is dependent primarily upon tension the net is under primarily in its longitudinal direction, but also in its widthwise direction as it is being deployed. Moreover, the balance between these forces directly impact the dimensions of the net as it is deployed. The balance or differences between these forces may vary dramatically along the length of the net such that the net is excessively wide along certain portions of the row of crops and excessively narrow along other portions.
This lack of dimensional stability makes it very difficult to simultaneously deploy or apply a knitted net in its design size, that is, both the correct length and correct width dimensions that would typically be marked on the label of the net. Workers installing the net attempt to apply the correct tension in the lengthwise and widthwise directions in order to achieve proper coverage of the net. Some nets include colored indicator lengthwise stripes to assist in installation. When the net is properly installed, the stripes will be a predetermined distance apart. However, this can be a slow and cumbersome process, particularly to repeatedly monitor the spacing to properly install the net.
The problems associated with installing current nets are most acute when the installation process places either excess or insufficient tension in the warp direction, that is, the lengthwise, direction. When over-stretched lengthwise, the net cannot be stretched widthwise to the dimension as marked on the label. The net will be too long in the lengthwise direction, and too short in the widthwise direction. Conversely, if workers under-compensate and place too little tension on the net in the lengthwise direction, the net will be too short in the lengthwise direction, and too long in the widthwise direction relative to the design size. As a result, nets would need to be sized larger than what is actually needed for the installation, to compensate for the less than optimal installation of the net. This can mean unnecessary higher costs for the nets.
There exists a need then for a net to protect fruit from bird damage that is inexpensive, and has ready guidance for optimal installation, that has rip stop construction, and that is supple and easily draped over fruit-bearing plants.